Carburetor



March 23, 1937.. c. H. KIRBY 2,074,749

CARBURETOR Filed March 18, 1933 2 Sheets-Sheet l CHAELES H. ,Z/eaY,

-March 3, 1937, c. H. KBRBY 2,074,749

CARBURETOR Filed March 18, 1933 2 Sheets-Sheet 2 Patented Mar. 23, 1937 UNITED STATES PATENT OFFICE CARBURETOR Application March 18, 1933, Serial No. 661,435

4 Claims.

This invention relates to carburetors for internal combustion engines and has special reference to simplifying the starting thereof under varied temperature conditions by providing an improved automatic control of the starting and warming up mixture as a substitute for the usual manual dash control of the choke valve.

It is an object of this invention to provide an improved and simplified automatic choke control to assist in starting a cold engine as well as to provide optimum warming up conditions by automatically graduating the choking effect l to the temperature of the engine and at the same time providing a faster idling speed for cold starting by increasing the available area of the idling bypass as the required choking effect increases in severity due to low temperatures.

It is another object of this invention to provide an improved and simplified control of the choking efiect and mixture bypass that will remove such controls from possible abuse by the operator, and yet fully compensate for variations in operating conditions which require different degrees and duration of choking effect and idling speed to secure prompt warming up of a cold engine without stalling thereof.

It is another object of this invention to provide an improved automatic choke and bypass control adapted to start an engine without opening the usual throttle control whereby an increased idling speed will be provided to offset unfavorable operating conditions, and in which the opening of the throttle, as when a load is applied to the engine, will be compensated for by an increased opening of the choke valve to prevent loading of the engine with an overrich fuel and air mixture.

This invention embodies a number of improvements over that disclosed in my copending application Serial No. 224,035, filed October 5, 1927, and which issued as Patent No. 1,919,470, on July 25, 1933.

Other and further important objects of this 5 invention will be apparent from the disclosures in the specification and the accompanying drawings.

This invention (in a preferred form) is illustrated in the drawings and hereinafter more ful- 50 ly described.

On the drawings:

Figure l is a side elevation of an internal combustion engine and manifolding system provided with a thermostatic choke control embodying the features of this invention.

Figure 2 is an enlarged fragmentary plan view of the manifolding system of Figure 1.

Figure 3 is an enlarged fragmentary elevation of the thermostatic choke control.

Figure 4 is an enlarged fragmentary section through the bypass valve taken on the line IV--IV of Figure 3 with parts omitted.

Figure 5 is a section on the line V--V of Figure 4.

Figure 6 is a fragmentary section, with parts 10 in elevation, of the choke valve levers taken on the line VI-VI of Figure 3.

As shown:

An internal combustion engine ill is shown in Figure 1 to illustrate a typical carburetor and 15 manifolding system comprising an exhaust heated riser l2 feeding an intake manifold lit, the riser jacket being fed exhaust gases from an exhaust manifold I4. The carburetor comprises generally a body member ll having an air in 20 take II, and a float bowl I provided with a fuel inlet 8. This showing is intended to be conventional, since the subject matter of this invention is not limited to updraft carburetors. nor in fact to a separate choke valve, because 26 the air valve type of carburetor chosen for illustration can be choked by a suitable control applied directly to the air valve instead of using a separate choke valve in the air inlet anterior to the air valve. 30

As shown, a throttle valve lever I5 is mounted on the outer end of a throttle shaft 16 which is located on the riser in preference to a location in the carburetor body, and carries the usual throttle valve (not shown). The throttle 35 shaft 16 carries a multiple arm device 6, one portion 6 of which is arranged to engage an abutment 5 on the riser l2 to determine the closed position of the throttle, another portion 6" of which is adapted for connection in a throt- 40 tle operated rod which is not shown, and a third portion 6 of which is connected by means of a link 4 to a fuel control valve member 4'. The particular location of the throttle shaft forms no part of the present invention but is mentioned at this point because the desired bypass passage I I has its intake I8 adjacent the table l9 surrounding and forming the venturi 20 for the low speed nozzle 2|. The bypass passage i'l preferably extends up through the riser 12 to an outlet 22 in the intake manifold I3, as by such an arrangement the fuel and air mixture in the bypass is heated by flowing through the heated riser and thus delivers a dry and stable mixture unlikely to condense upon delivery to 5' the carburetor nozzles.

a cold manifold. While the long heated passage I1 is desirable, the passage may discharge into the riser or manifold at any point above the throttle, the essential feature being that the outlet 22 thereof is subjected to manifold suction above the throttle, which suction, as is well known, is a maximum under idling conditions when the suction within the carburetor is often ineffective to properly deliver and mix fuel from This, as well as other features of the carburetor, are disclosed in the above mentioned copending application,

The bypass inlet I8 is controlled by a sleeve valve 23, best shown in section in Figures 4 and 5. A side outlet port 24 is aligned with the passage I! to fully open the same and the valve is also slightly notched as at 25 in Figure 5 to maintain a restricted opening even when the valve is turned to its closed position. By main- 20 taining a slight circulation through the bypass passage at all times, stabilization and quick response to an opening movement of the valve is secured, since quick response to valve movements is obtained if there is a moving column of fuel and air mixture in the passage prior to opening of the valve. The outer end 23' of the sleeve valve 23 projects outwardly from the body member H, as shown most clearly in Fig. 4 and is secured to an arm 35.

The carburetor air inlet horn 26 is provided with an unbalanced butterfly choke valve 21 mounted on a shaft 28 offset to one side of a major diameter of the air inlet in such a way that high suction acting ,on the unbalanced choke valve tends to open the valve against the resistance of a spring 29 (Fig. 6) tending to cause an arm 30, rigidly mounted on the valve shaft 23, to follow a floatingly pivoted lever crank arm 3| as the latter is moved toward a valve closing position, the crank arm 3| being operated by a lever 33. The lever arm 32 is provided integral with the arm 30, the arm 32 being connected by a link 34 to the arm 35 on the bypass valve 32, the arrangement being such that the bypass valve is fully open when the choke valve is closed and is closed, except for the notch 25, when the choke valve is open. The rigidly mounted arm 30 has a lug 36 yieldingly held against the arm 3| by the spring 29 so that when the arm 33 is rotated in a counterclockwise direction by a thermostatic control, the unbalanced choke valve yieldingly follows the arm 3|. However, high suction developed against the closed unbalanced valve tends to rotate the valve and arm 30 in a clockwise direction away from the arm 3| and this movement is yieldingly limited by a spring biased plunger 31 in an integral offset 38 of the arm 30. The foregoing described choke valve structure per se is substantially similar to that disclosed in the application of David Firth, Serial No. 575,720. filed November 19, 1931 entitled Automatic choker valve, which matured into Patent 1,966,201, granted July 10, 1934.

The choke valve operating lever 33 is linked by a rod 39 to the free end 40 of a thermostatically operated lever which is pivoted at 42 in a housing 43 mounted on the exhaust manifold. The housing contains a coiled bi-metallic thermostat 44 anchored at one end in an adjustable mounting 45 and carrying a crank arm 46 at the other end which is pivoted at 41. The lever 46 engages a pin 48 on the crank arm 4| to move the latter. As shown, the thermostat is intended to coil up in a clockwise direction with volves opening the choke valve upon the engine,

reaching the desired operating temperature and closing the valve in proportion to the" cooling of the engine to provide an increased flow of mixture under unfavorable operating conditions.

Operation When the engine has been out of use for a suflicient time to cool off, the thermostat 44 tends to uncoil in a counter-clockwise direction and force the lever 4| downwardly acting through the rod 39 to move the choke valve into its closed position. Such movement of the choke valve also opens the bypass valve 23 by means of the arm 32, link 34 and arm 35. Subsequent starting of the engine will then involve only closing the ignition and starting motor switches to rotate the engine crankshaft, whereupon the closed choke sets up the desired high suction on the usual fuel orifices and the open bypass feeds the resulting rich fuel and air mixture into the intake manifold above the throttle. The bypass prevents cutting oil? the supply of fuel and air mixture should the throttle remain closed during the starting operation. The action of the bypass, when fully open, serves to increase the engine idling speed to that equivalent to a vehicle speed as high as 15 or 18 miles per hour in direct drive, the exact increase being of course subject to choice by a suitable design of the bypass area. a

As the thermostat operates, through temperature increases due to warming up the engine, to gradually open the choke valve, the bypass continues to function at a proportionately decreased rate until the bypass valve reaches its limit of closing movement when the notch 25 still permits a minimum flow adapted to stabilize idling conditions at the minimum idling speed desired with a motor thoroughly warmed up.

If the throttle were to be opened while the choke valve was still substantially closed, the increased suction on the unbalanced valve would cause the same to open moving the lever 3| towards the yielding stop 31 in opposition to the spring 29, thus admitting suflicient additional air to allow the engine to carry a substantially normal load without excessive over-enriching of the fuel and air mixture with consequent loading of the engine.

It will thus be seen that I have invented an improved thermostatic choke and bypass control adapted to automatically supply a proper fuel and air mixture to an internal combustion engine for starting and warming up the same and wherein the idling speed of the engine is automatically increased to overcome unfavorable operating temperatures which would cause stalling at the low idling speeds desirable and satisfactory for use with a warm engine.

I am aware that many changes may be made and numerous details of construction may be varied through a wide range without departing from the principles of this invention, and I, therefore, do not purpose limiting the patent granted hereon otherwise than necessitated by the prior art.

I claim:

1. In combination with a carburetor for an internal combustion engine, including a choke valve and a throttle valve for said carburetor, a bypass passage around said throttle valve location, the discharge end of said passage being subjected to the suction above the throttle while the inlet end of said passage is so positioned relative to the carburetor fuel delivery nozzles as to pick up a rich fuel and air mixture therefrom, a valve controlling said bypass passage, operating linkage connecting said valve to the choke valve to open said valve when the choke valve is closed, thermostatic means responsive to temperature variation and operating linkage from said thermostatic means to said choke valve, the thermostatic means being arranged to close said choke valve and thereby open said bypass valve at low temperatures and to open said choke valve at normal operating temperatures.

2. In combination with a carburetor for an internal combustion engine, including a choke valve and a throttle valve for said carburetor, a bypass passage around said throttle valve location, the discharge end of said passage being subjected to the suction above the throttle while the inlet end of said passage is so positioned relative to the carburetor fuel delivery nozzles as to pick up a rich fuel and air mixture therefrom, a valve controlling said bypass passage, said valve being slightly open at all times to stabilize the mixture ratio at low idling speeds, operating linkage connecting said valve to the choke valve to open said valve when the choke valve is closed, thermostatic means responsive to temperature variations and operating linkage from said thermostatic means to said choke valve, the thermostatic means being arranged to close said choke valve and thereby open said bypass valve at low temperatures and to open said choke valve at nor- 49 mal operating temperatures.

3. In combination with a carburetor and a manifolding system for an internal combustion engine, including a choke valve and a throttle valve for said carburetor, a bypass passage around said throttle valve location, the discharge end of said passage being subjected to the suction above the throttle while the inlet end of said passage is so positioned relative to the carburetor fuel delivery nozzles as to pick up a rich fuel and air mixture therefrom, a valve controlling said bypass passage, operating means having a yielding connection to the choke valve to permit partial opening of said valve in response to suction thereon, linkage connecting said operating means to the bypass valve to open said bypass valve when the choke valve is yieldingly closed, and thermostatic means arranged to operate the choke valve in accordance with temperature conditions.

4. In combination with a carburetor and a manifolding system for an internal combustion engine, including a choke valve and a throttle valve for said carburetor, a bypass passage around said throttle valve location, the discharge end of said passage being subjected to the suction above the throttle while the inlet end of said passage is so positioned relative to the carburetor fuel delivery nozzles as to pick up a rich fuel and air mixture therefrom, a valve controlling said bypass passage, said valve being slightly open at all times to stabilize the mixture ratio at low idling speeds, operating means having a yielding connection to the choke valve to permit partial opening of said valve in response to suction thereon, linkage connecting said operating means to the bypass valve to open said bypass valve when the choke valve is yieldingly closed, and thermostatic means arranged to operate the choke valve in accordance with temperature conditions.

CHARLES H. KIRBY. 

